According to the gas station's website, here's how the sign came about:

"In October of 2005 we converted our auto repair shop into an ExtraMile convenience store and suddenly we had a problem. It had always been easy to think of useful messages to put on the sign for things like service promotions and store specials and the like. But with the ExtraMile, there were no more cars to fix and the place was plastered with store specials."

If you can't visit the sign, that's fine. You can following the Wallingford Sign's updates onFacebook and Twitter.